14 C.F.R. § 125.133 Fuel valves.
Title 14 - Aeronautics and Space
Each fuel valve must— (a) Comply with §125.155; (b) Have positive stops or suitable index provisions in the “on” and “off” positions; and (c) Be supported so that loads resulting from its operation or from accelerated flight conditions are not transmitted to the lines connected to the valve.
Title 14: Aeronautics and Space
PART 125—CERTIFICATION AND OPERATIONS: AIRPLANES HAVING A SEATING CAPACITY OF 20 OR MORE PASSENGERS OR A MAXIMUM PAYLOAD CAPACITY OF 6,000 POUNDS OR MORE; AND RULES GOVERNING PERSONS ON BOARD SUCH AIRCRAFT
Subpart E—Special Airworthiness Requirements
§ 125.133 Fuel valves.